Brook-Claisen rearrangements

The discovery in 1971 that allvl pentafluorophenyl ether (22a) rearranges in the vapor phase at 365 C to 4-allyl-2,3.4,5,6-pentafluorocyclohexa-2.5-dienone (24a)19 marked the beginning of intensive and fruitful studies into the Claisen and hetero-Claisen rearrangements of arenes and hetarenes, studies which have been reviewed concisely by the principal investigator of this chemistry. G.M. Brooke.2"... 

Woodcock HL, M Hodoscek, P Sherwood, YS Lee, HF Schaefer, BR Brooks (2003) Exploring the quantum mechanical/molecular mechanical replica path method a pathway optimization of the chorismate to prephenate Claisen rearrangement catalyzed by chorismate mutase. Theor. Chem. Acc. 109 (3) 140-148... 

A tandem Brook and Claisen rearrangement of cyclopentenyl derivative 29 has been applied to the synthesis of naturally occurring sesquiterpene (a- )-ophiobolin C. The Ireland rearrangement of 29 results in substantial formation of C-silylated product543. 

In their total synthesis of (-i-)-ophiobolin in 1989, Kishi et al. found that treatment of a cyclopentenyl ester under the typical Ireland conditions gave principally C-silylated ester [63]. Heating of a C-silyl ester (prepared by acylation using a C-silyl acyl chloride) at 230 °C resulted in a 1,3-Brook rearrangement followed by an Ireland-Claisen rearrangement to give the desired product as a 6 1 ratio of isomers at C2 of the pentenoic acid (Scheme 4.63). The major product could have arisen through either a chair transition state of the Z-sUyl ketene acetal or a boat transition state of the E-silyl ketene acetal. 

Brooke GM Ferguson JAKJ (1986) Partially fluorinated heterocyclic compounds. Part 22. The preparation of allyl 2,5,6-trifluoropyrimidin-4-yl ether and related compounds and a study of their Claisen rearrangement reactions. A new route to 5-fluorouracil and barbituric acid derivatives. J Chem Soc Perkin Trans 1 515-520... 

---